Why is Maggie so Murky?

Dredging in Cleveland Bay. Source: MINCA.org

Hello Islanders, Townsvillians, and fellow snorkellers of the North Queensland region.

If you’re anything like me, you often look forward to escaping the city to explore our local piece of paradise on the weekends.

But sometimes, we may be disappointed that despite the weather being clear and sunny, a snorkel often isn’t possible on Magnetic Island.

I used to think that poor visibility was just the nature of all inshore reefs. But after talking to a few locals, I was soon convinced that there had to be another factor at play.

So I decided to do some researching, and I began by looking back in time.

Apparently, in the 1960s, the visibility on Maggie was typically more than 10m, particularly in Arthur and Florence Bays. In fact, biologists have compared the reefs on the island to those found on the outer reef!

The Island’s “coastal fringes once supported coral reefs equal to any found on the Reef proper” —Theo Brown (1972).

But today, visibility on Maggie rarely exceeds 2m (MINCA.org). This just didn’t seem right. After some investigation, I found that the answer was glaringly clear:

From the early 1970s onwards, the shipping channel in Cleveland Bay was expanded. During this time, the Townsville Port obtained authority to dump dredge material at a new site, just east of the island.

Answer: Dredge sludge from the Townsville Port is placed right next door to our local reefs

Expansion of the shipping channel to the Port of Townsville is conducted to provide greater access to the port, particularly for larger vessels. Unfortunately, this means that maintenance dredging must occur for 4-5 weeks per year.

The blue line shows the extended dredged channel to the Port, while the Dredge Material Placement Area (DMPA) shows the location of where the majority of maintenance dredge is dumped. The DMPA is located just 4km East of the pristine reefs of Magnetic Island!

Unfortunately, winds in Cleveland Bay predominantly come from a south-easterly direction. When wind stirs up sediment, silt pollution from the dredge is blown into the bays of Magnetic island, destroying the visibility for local divers and holidayers alike.

In fact, prior to any major dredging of the channel, the Queensland Department of the Environment established a popular reef trail in Geoffrey bay. This was used as a recreational and educational attraction, where visitors could walk along the reef flat with a map, finding a diverse range of species including branching and brain corals (MINCA.org).

Today, the walking trail has been long abandoned, and the intertidal reef is covered in a layer of mud. Whatever the complex reasons for these declines, near-shore fringing reefs and sea grass beds along the Queensland coast are fast disappearing and they can ill-afford further cumulative impacts from unprecedented dredging programs.

—Professor Terry Hughes, Director of the ARC Centre of Excellence for Coral Reef Studies (2014).
Source: MINCA.org

This Port was designed under the Sustainable Ports Development
Act 2015.
But maintenance dredge is continuously dumped just next-door to our island. Annual dredging has known devastating effects on our coral reef ecosystems and is not sustainable for our natural ecosystems.

No plans to stop dumping dredge in the sea

The Townsville Port have a long-term maintenance dredging plan in place, where they plan to continue dumping their maintenance dredge in the same place. Dredging has been found to decrease light levels and decrease coral calcification (growth) by up to 33% (Bak 1978), resulting in the annual smothering of the reefs surrounding our island.

While other ports around Australia have decreased their amount of dredging, the Townsville Port plans to increase their dredging over the next 10 years. The Port is expecting to dredge approximately 6,050,000m³ to maintain the channel from 1 January 2019 to 1 January 2029, and dump a majority of this sediment in Cleveland Bay. See the 10-year plan below:

The Port gets special treatment

Even more frightening, is that the Townsville Port and shipping channel are somehow exempt from being a part of the Great Barrier Reef Marine Park. Below, we can see an imaginary boundary which has been drawn as an “exclusion area” from the World Heritage Site, despite being located just 1km from Bremner Point on Magnetic Island.

This means that the port is somehow “excluded” from being protected under the Great Barrier Reef World Heritage Area that surrounds it.

The marine life in this region of the shipping channel are totally disregarded from any protection awarded to the Great Barrier Reef, our World Heritage Listed site.

On their website, the Port of Townsville can therefore say that the dredging “Has no direct impact in the Great Barrier Reef Marine Park General Use Zone.”

But unfortunately, the circulatory nature of the ocean does not quite work in this way. We cannot simply build a fence, or draw a line and remove protection from parts of the ocean without expecting there to be nearby repercussions.

Dredge silt being dumped in the DMPA is blown straight towards the island from any easterly or southeasterly winds. Here, it settles on our pristine reefs of Geoffrey, Arthur and Florence Bay.

Partially dead coral colonies covered in silt on Magnetic Island’s reefs. (Reef Check Australia 2008)

Further Cleveland Bay is home to a plethora of marine plants, animals and birds. Many species reside here, including Snubfin Dolphins, humpback dolphins, turtles and dugongs.

Dredging poses a danger to our native and endemic species

The Snubfin Dolphin is Australia’s only endemic dolphin. There is believed to be only thousands of them remaining and they are listed as Vulnerable by the IUCN Endangered Species list.

Australia’s Snubfin Dolphin: Source: MINCA.org

The only reliable local estimate of population size of Australian Snubfin Dolphins is located right here, in Cleveland Bay. There has been estimated that a population of around 100 individuals inhabits our local backyard (Parra et al. 2002; Australian government, 2020).

Continuous dredging will further decimate the habitat of these dolphins, having disastrous results for the species.

A report funded by the Townsville Port Authority stated that:

“The dumping of very large quantities of dredged sediment in the early and mid 1970s probably played a significant part in more widespread changes to the seagrass beds throughout the Cleveland Bay area” (Pringle 1989, pg 74).

But the report also said we should continue to monitor these effects.

Unfortunately, non-action is not quite good enough. Seagrass habitats are vital for the survival of not only Snubfin dolphins, but also dugongs and turtles, both which have been observed in Cleveland Bay.

Green Sea Turtle at Arthur Bay: by Tiani Dun

Why are we letting the port “Continue to monitor” the effects of dredging on our endangered species? We already know that dredging in other areas causes habitat loss, which is detrimental for entire ecosystems (Todd et al. 2015, Wilber and Clarke 2000, Gintert et al. 2019, Okoyen et al. 2020, Erftemeijer et al. 2012, Pollock et al. 2016, Brown et al. 1990, Dodge and Vaisnys 1977, just to name a few studies!). Do we really need further studies to show this same effect on a local scale?

By the time these studies find what they are looking for, it will already be too late for our marine species’ populations.

Since the 1883 Townsville Port have been dredging a shipping channel in the harbour. Prior dredge was dumped in Middle Reef near Cockle Bay, creating the wasteland we see today.

Accumulative affects of a long history of dredging combined with the already muddy sediment bottom of Cleveland Bay resulted in devastating impacts during cyclone Yasi. With dredging only looking to increase, along with a predicted increase in natural disasters, future impacts are likely to be alarming.

It appears that it is up to us, the community members and ocean advocates, to step up and have our voices heard.

A simple solution to this issue would be to simply relocate the DMPA site further offshore where it would not be blown onto our local reefs.

But instead of coming up with a solution to this environmental issue, the Port of Townsville funds projects such as the MOUA, which will set up a snorkel trail on the island that is pointless if the visibility is continually ruined by the dredge.

How can we expect to save the planet if we can’t even protect the local reefs in our back pockets?

It is time we unite and stand up to protect our island home!

What can we do?

Write to our Australian Minister for the Environment:

I have drafted up a letter which you can send to our Environmental Minister, Sussan Ley. You can copy and paste the template below and submit your concern online here:

Dear Sussan Ley,

I wish to formally submit my opposition to the placement of the DMPA site by the Port of Townsville, just 4km east of Magnetic Island.
In particular, I am concerned about the dredge spoil and its affect on our local reefs on Magnetic Island.

I believe that objectives and purpose of the marine park, which is to protect and conserve the Reef, are not being met as annual dredging continues to smother the corals and their inhabitants each year.

My main concerns overall are:
– Talk about your main concerns here: ie. visibility, tourism, ethics, turtles, dugongs, etc.

Finally, I believe that this issue can be easily resolved by relocation of the DMPA further offshore where it will not have such localised impacts on Magnetic Island.

Your name. 

You can also send the same letter via email to the Queensland Environmental Minister Meaghan Scanlon here, or express your concerns to GBRMPA (assessments@gbrmpa.gov.au) and the Port of Townsville (community@townsvilleport.com.au).

Students: Be wary of who you work or intern for and who they are affiliated with. Do your research to see who funds your professor’s projects!

Let’s not let large industries smother our beloved local reefs right in front of our noses.

I don’t know about you, but I want my children to be able to snorkel in some clear water here on Magnetic Island.

Further Reading:
Keeping our Great Barrier Reef Great
Environmental and Social Values Surrounding the Port of Townsville
Port of Townsville Limited Long‐Term Maintenance Dredging Management Plan
Port of Townsville Seagrass Monitoring Program
Maintenance Dredging Fact Sheet

5 Thoughts on “Why is Maggie so Murky?

  1. You do realise they no longer dump dredge waste in the water yeah? Not in this local area. You are 100% right about the dredge waste for the old channel dredge days and it’s been on the ocean charts listed for everyone to see since it was dredged in the first place.
    I am definitely against dredging when the sludge mud and silt is dumped where it hasn’t naturally settled but you also have to take into account that the entire Cleavland bay is also a very shallow area no more than 5-6m deep the entire time over such a vast area of sea floor.
    Take somewhere like cungulla for example, also bowling Green bay where another vast area of shallow sea floor resides and has a natural mud/sand mixture, when areas such as this experience wind turbulence when the water is so shallow the water gets murky very quickly and you will notice that in regards to Cleavland bay on a s/W offshore wind the bay clears up because the wind doesn’t have enough water surface area to stir the mud and silt whereas on a north/east it South/east the winds have a large unobstructed length in which to stir the mud and silt easily.
    No one is denying that the dredge mud that was dumped out in the bay was unnecessary (now when they dredge they captive tailings in land reclaim) but to say that it’s the cause is a bit nieve.
    Places like the palm group of island well anywhere north of Maggie if you draw a line from Cape Cleavland to Maggie north side then to Cape pallarenda anywhere north of there and you have deep water 15-20 right up to 35m and the islands pop up out of that deep water and the water quality is far beyond anything Maggie can expect to see nor Cleavland bay….

  2. It’s absolutely discussing what humans will do for profit. I’ve seen the destruction of the reef at Nelly and have spoken to elderly residents who say that it was beautiful before the dredging started. We need to keep these politicians accountable. Keep up the good work

    1. Thanks Janeen. The first step is raising awareness, and then we can be mindful of our actions and who we support! We all need to be aware of these injustices so we can stop being part of the problem and become a part of the solution. 💪💚🌏

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